Grinding arrangement

ABSTRACT

A grinding arrangement for sharpening knives carried by a chopper drum includes a movement arrangement for moving a grinding stone along the chopper drum during a grinding process. A force measurement arrangement is provided which measures the force applied to the knife by the grinding stone, during the grinding process, and provides a signal representing this force for controlling a movement arrangement which moves the grinding stone as a function of the signal received from the force measurement arrangement. The manner of measuring the force is by way of a force measurement cell inserted in the power flux connection between the grinding stone and the chopper drum.

FIELD OF THE INVENTION

The invention concerns a grinding arrangement with a grinding stone for grinding at least one knife of a chopper arrangement, a movement arrangement for moving the grinding stone along the chopper arrangement, a measurement arrangement for the provision of a signal that contains information regarding the force applied by the grinding stone of the knife during the grinding process and a control arrangement that controls the movement arrangement as a function of the signal of the measurement arrangement.

BACKGROUND OF THE INVENTION

During the operation of a forage harvester, the knives fastened to the chopper arrangement wear over time. It is possible that individual knives wear at different rates. While the knives around the circumference of the chopper arrangement as a ruled wear at approximately uniform rates, the wear along the width of the chopper arrangement may vary considerably. Thereby, the diameter of the enveloping circle described by the cutting edges of the knives can vary in the axial direction of the shaft of the chopper arrangement. A cylindrical or slightly concave shape is desired as a target shape in order to simplify the automatic repositioning of the shearbar or in order to make this possible depending upon the repositioning system. A parallel and precise in-feed of the shearbar towards the circumference of the chopper arrangement is indispensable for a effective chopper process.

To avoid this problem, U.S. Pat. No. 6,503,135 proposes that the actual shape of the enveloping circle described by the knives of a chopper arrangement be detected before a grinding process and to thereupon move the grinding stone on the basis of the results of the measurement in such a way that a desired shape of the enveloping circle is attained. The shape of the enveloping circle is detected by means of a knock sensor or by a magnetic sensor associated with the grinding stone or with the shearbar. As an alternative, the force applied to the shearbar is measured.

The disadvantage of a measurement of the spacing between the shearbar and the knives by means of magnetic sensors, knock sensors or force sensors is seen I the fact that an additional information about the immediate angle of rotation of the chopper arrangement is required in order to be able to associate the immediate measurement value of the spacing with the particular knife. Moreover, at high rotational speeds, the association with the proper knife may be problematic. In addition, an improper positioning of the shearbar that is not parallel to the shaft of the chopper arrangement may adversely affect the validity of the measurement. If the spacing at the grinding stone is detected inductively or by a knock sensor, there are problems with the association of the measurement values with an actual spacing, since the vibratory performance of the grinding stone and the noises generated by it are a function of its worn condition. Inductive measurement processes depend upon the condition of the knives and are therefore also problematic.

The problem underlying the invention is seen in the need to make available a grinding arrangement that is improved relative to the state of the art, in which the problems cited above do not exist or do so only to a lesser degree.

SUMMARY OF THE INVENTION

According to the present invention, there is provided an improved grinding arrangement for grinding knives of a chopper arrangement.

An object of the invention is to provide a grinding stone arrangement which has its movement relative to cutting knives controlled by signals representing the force applied by the grinding stone to the knives.

The invention proposes that a force measurement cell be attached to any desired location in the connecting line or power flux connection between the grinding stone and the chopper arrangement. The force measurement detects the load or the pressure exerted by the grinding stone on the knife or knives of the chopper arrangement during the grinding process. The value measured by the force measurement cell is all the greater when the enveloping curve of the knives is closer to the grinding stone and the smaller when the knives are separated from the grinding stone.

In this way, the result is an absolute and exact measurement value that contains information about the actual shape of the knife. The chopper arrangement can be brought into an optimum shape tat makes possible the repositioning to a sufficiently small cutting gap. Thereby the energy required for the chopper operation can be reduced or at a constant energy level a higher throughput can be attained. Furthermore, the quality of the chopper operation or the length of cut is improved (that is, the uniformity and precision of the cut). The proportion of uncut components, such as husks or leaves, is sharply reduced or even eliminated.

The movement arrangement for the grinding stone is controlled by the control arrangement in such a way that the grinding stone brings the cutting edge of the knife into a certain target shape which may be a predetermined shape or a shape that can be selected from several inputs or from any desired input shape. In order to attain the target shape of the cutting edge of the knife, the control arrangement can perform a comparison between the information made available by the measurement arrangement regarding the actual present shape of the cutting edge and the target shape and control the movement arrangement as a function of the result of the comparison. Thereby, the grinding stone is controlled by the movement arrangement that transports the grinding stone across the width of the chopper arrangement and provides an in-feed as a function of the signal of the measurement arrangement and brings about a movement of the grinding stone in such a way that any deviation in the shape of the cutting edges of the knives is automatically equalized.

The chopper arrangement may include a chopper drum in open or closed form to which several knives are attached. The chopper drum is arranged on a shaft that is brought into rotation during the grinding and in its normal operation, as a rule, rotates in the opposite direction compared to the normal chopper operation. In the case of chopper drums of this type, the measurement arrangement detects information about the distance between the shaft and the cutting edges of the knives, that is, the radius of the enveloping circle described by the cutting edges. However, the invention can also be applied to chopper arrangements with web disk wheel choppers. There it is not the radius of the cutting edges of the knives that is detected, but their axial position.

The force measurement cell can be attached between the grinding stone retainer of the grinding stone and a frame to which the grinding stone retainer is fastened and that also carries the chopper arrangement. As a rule, the grinding stone retainer can be traversed across the width of the chopper arrangement and is supported in bearings on a shaft. The force measurement cell may be arranged between the shaft and the frame or between the shaft and the grinding stone retainer.

Alternatively, or in addition, there is the possibility of arranging the force measurement cell between the grinding stone and the grinding stone retainer.

Furthermore, the control arrangement can make an error signal available in case the measured force that is applied to the grinding stone exceeds a threshold value. This error signal can be provided to the operator optically or acoustically and points to a knife projecting too far outward. Moreover, in this case the grinding process can be stopped automatically. Thereby, damage (breaking out) or unusual wear of the grinding stone can be avoided, since in the case of excessive force between the grinding stone and the drum countermeasures are taken.

The present invention can be applied to a multitude of arrangements with knives that must be sharpened. It can be used in particular on self-propelled or towed harvesting machines with chopper drums or web disk wheel choppers.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings show two embodiments of the invention that shall be described in greater detail in the following.

FIG. 1 is a schematic left side view of a harvesting machine with a chopper arrangement.

FIG. 2 is a front view of a first embodiment of a grinding arrangement.

FIG. 3 is a front view of a second embodiment of a grinding arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The harvesting machine 10 shown in FIG. 1 in the form of a self-propelled forage harvester is supported on a frame 12 that is carried by front and rear wheels 14 and 16. The harvesting machine 10 is controlled from an operator's cab 18 from which a harvested crop take-up arrangement 20 can be seen. Crop taken up from the ground by means of the take-up arrangement 20 can be seen. Crop taken up from the ground by means of the take-up arrangement 20, for example, corn, grass or the like, is conducted to a chopper arrangement 22 in the form of a chopper drum, which chops it into small pieces and delivers it to a conveyor arrangement 24. The crop leaves the harvesting machine 10 to an accompanying trailer over a discharge duct 25 mounted for being selectively rotated about an upright axis. A post-chopper reduction arrangement 28 extends (during the corn harvest) between the chopper arrangement 22 and the conveyor arrangement 24 through which the crop to be conveyed is conducted tangentially to the conveyor arrangement 24.

FIG. 2 shows a schematic view of a chopper arrangement 22 and a grinding arrangement 26 associated with it, as it is seen when looking at the harvesting machine 10 in FIG. 1 from the front (relative to the direction of operation). The chopper arrangement 22 is provided with a number of knives 38 distributed over its width at its circumference which cut harvested crop taken up by the harvested crop take-up arrangement 20 in interaction with a rigid shearbar 46. The chopper arrangement 22 includes a central shaft 32, that can be driven in rotation by means of a belt pulley 36 at its end face and belts, not shown, by a motor of the harvesting machine 10. The shaft 32 is supported by two rolling contact bearings 56 arranged on both sides of the chopper arrangement 22 on the frame 12 of the harvesting machine 10.

In order to be able to sharpen the knives 38 after a certain operating time, without having to disassemble the individual knives 38 or the entire chopper arrangement 22, the grinding arrangement 26 is provided above the chopper arrangement 22 near the enveloping circle described by the knives 38. The grinding arrangement 26 essentially includes a grinding stone 42, a grinding stone retainer 40 associated with it and a support shaft 44 oriented parallel to the shaft 32, on which the grinding retainer 40 is supported in bearings, free to slide.

If the knives 38 are to be sharpened, the chopper arrangement 22 is brought into rotation, as a rule in the opposite direction of rotation and/or at a reduced rotational speed, compared to the normal chopper operation. The grinding stone retainer 40 with the grinding stone 42 attached to it is shifted across the entire width of the chopper arrangement 22 by means of a movement arrangement 48 from a rest or park position, not shown, in which it is arranged at the side alongside the chopper arrangement 22. Thereby, the underside of the grinding stone 42 is in contact with the knives 38 and sharpens them. During the grinding process, the grinding stone 42 traverses several times across the width of the chopper arrangement 22. The end points of this sliding movement are illustrated in FIG. 2 by the grinding stone retainers with the part number call-out 40 at the left reversal point and 40′ at the right reversal point.

Between the sliding traverse movements, an in-feed of the grinding stone 42 can be performed, that is a small movement of the grinding stone 42 towards the knives 38. In the embodiment shown for this purpose, a mechanical element (ratchet wheel) is used that interacts with an element fixed to the frame when one or both of the reversal points of the grinding stone retainer 40 are reached. The rotation of the mechanical element is converted into a sliding movement by means of a screw thread, so that the grinding stone 42 is provided with an in-feed towards the chopper arrangement 22. When the grinding stone 42 is shifted only over a limited sideways shift region, an in-feed movement can be avoided, since then the mechanical element does not come into contact with the stationary element. A grinding of this type without in-feed is appropriate for the honing at the end of the grinding process.

The movement arrangement 48 of the grinding arrangement 26 is controlled by a control arrangement 52, shown schematically in FIG. 2 which controls the shifting of the grinding stone 42 by the movement arrangement 48 as well as the in-feed in the manner described above. The control arrangement 52 is supplied with information about the immediate position of the grinding stone 42, this can be provided by a corresponding sensor 58, which detects the immediate position of the movement arrangement 48, or that the control arrangement 52 has been supplied with information into which position it has brought the grinding stone retainer 40. For this purpose, for example, the number of impulses can be stored in memory that have been delivered to a stepper motor of the movement arrangement 48. In addition, the control arrangement 52 can control the drive of the chopper arrangement 22.

It should be noted that the in-feed could also be performed by a separate motor, particularly an electric motor or a hydraulic motor, that would also have to be connected with the control arrangement 52. In place of an in-feed by moving the grinding stone 42, the entire grinding stone retainer 40 or the shaft 44 could be moved in the in-feed direction.

The control arrangement 52 is connected with a memory 54 and with two force measurement cells 50, that are used as a measurement arrangement. The force measurement cells 50 are arranged close to both ends of the shaft 44 between the shaft 44 and the frame 12 or an element connected to it. The force measurement cells 50 may be of any desired configuration, such as piezo-electric sensors or strain gages. They deliver a measurement value to the control arrangement 52, that is proportional to the force applied to the knives 38 by the grinding stone 42 or the reverse. this force contains information regarding the enveloping curve described by the knives 38 on the immediate position of the grinding stone 42. If the grinding stone retainer 40 is supported on two parallel shafts 44, each of the shafts 44 can be associated with two force measurement cells 50 at the ends, or the two shafts 44 are connected to each other at both ends and supported in each case on the frame over a single force measurement cell 50. The use of a single shaft 44 is also conceivable that has a non-circular cross section (for example, a rectangular cross section).

A grinding process can take place as described in the aforementioned U.S. Pat. No. 6,503,135. After the beginning of the grinding process, the control arrangement 52 brings about a traverse across the width of the chopper arrangement 22 by the grinding stone 42 by means of the movement arrangement 48, and then is again traversed back into the original position. Thereby, the grinding stone 42 can remain in the position into which it was brought during the preceding grinding process, or, if necessary, provided with an in-feed towards the chopper arrangement 22. This process can be used to determine whether an in-feed of the grinding stone 42 is required. This is the case if no signal (or a relatively minor signal) is generated by the force measurement cell 50 in at least one location of the chopper arrangement 22. In this case, there is an indentation, recess or the like in the knives 38, that cannot be removed or equalized without an in-feed. This process can also be omitted, particularly if a control is performed subsequently to determine whether the grinding process was successful.

During the traverse of the width of the chopper arrangement 22, the force measurement cell 50 generates a signal that is a function of the spacing between the cutting edges of the knives 38 and the grinding stone 42. The control arrangement 52 is supplied with information over an appropriate analog digital converter about the amplitude of this signal.

At first, the grinding stone 42 is not in-fed any further and is brought to a first position at the chopper arrangement 22, as a rule at the left or right outside. It remains in this position until the force measurement cell 50 generates an output signal that corresponds to a desired force between the grinding stone 42 and the cutting edges of the knives 38, so that a sufficient sharpness is attained by the parts of the knives 38 that interact with the grinding stone 42. After that, the grinding stone 42 is transported by the movement arrangement 48 through a distance corresponding to its width further to the left or the right and grinds the knives there. In this way, the entire width of the chopper arrangement 22 is processed successively. As a rule, the process described is repeated and/or performed multiple times at a reversed direction of movement. At the conclusion of the grinding process, a normal grinding and/or honing of the entire chopper arrangement 22 can be performed in a manner known in itself. Finally, the grinding stone 42 is brought into its park position.

A grinding process alternative to that described above is performed in such a way that the grinding stone 42 continuously traverses the entire width of the chopper arrangement 22, until a constant spacing between the shaft 32 and the cutting edges of the knives 38 is attained. The control arrangement 52 can recognize from the output signal of the force measurement cell 50, whether a constant spacing between the shaft 32 and the cutting edges of the knives 38 has been reached, and that corresponding thereto the grinding process can be ended. In this move, and in-feed of the grinding stone 42 can be performed, if the force measurement cell 50 does not detect a contact between the grinding stone 42 and the knives 38 at one or more places of the chopper arrangement 22.

To control the success of the operation or since the grinding stone 42 wears down during the grinding, which can result in an unsatisfactory result of the grinding process, the control arrangement can traverse the grinding stone retainer 40 one more time before the honing or during a subsequent normal grinding process across the width of the chopper arrangement 22 and detect the space in between the shaft 32 and the cutting edges of the knives 38 by means of the force measurement cell 50. If the shape of the cutting edges of the knives 38 is unsatisfactory here, a new grinding process is performed in the manner described above.

FIG. 3 shows a second embodiment of a grinding arrangement 26 according to the invention. Components that correspond to those of the first embodiment are designated by the same part number call-outs. There is a difference regarding the force measurement cell 50 that is arranged between the grinding stone 42 and the grinding stone retainer 40 in the embodiment according to FIG. 3. Here the force measurement cell 50 also delivers information regarding the force applied by the grinding stone 42 to the knives 38. The control arrangement 52 controls the movement arrangement 48 as a function of this information in the manner described above. The electrical connection between the force measurement cell 50 and the control arrangement 52 can be performed by a flexible cable or by a contact strip located on the shaft 44 connected with the control arrangement 52, which is fixed to the frame and electrically insulated from the shaft 44, with which a second contact strip on the grinding stone retainer 40 interacts, this is connected with the force measurement cell 50. Alternatively, a radio frequency connection is provided between the force measurement cell 50 and the control arrangement 52.

Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims. 

1. In a grinding arrangement including a grinding stone for the grinding of knives of a chopper arrangement, a movement arrangement coupled to the grinding stone and operable for selectively moving the grinding stone along said chopper arrangement, a measurement arrangement that makes available a signal that contains information about a force applied by the grinding stone to said knives during a grinding process, and a control arrangement that controls said movement arrangement as a function of said signal of said measurement arrangement, the improvement comprising: said measurement arrangement including a force measurement cell that is inserted into a power flux connection between said grinding stone and said chopper arrangement.
 2. The grinding arrangement, as defined in claim 1, wherein said control arrangement for controlling the movement arrangement includes a memory in which is stored a representation of a desired target shape of a profile of said knives when properly sharpened; and said control arrangement controlling said movement arrangement in such a way that cutting edges of said knives are brought into said desired target shape during said grinding process.
 3. The grinding arrangement, as defined in claim 1, wherein said grinding arrangement includes a grinding stone retainer holding said grinding stone; said grinding stone retainer being mounted to a support frame; and said force measurement cell being inserted between said grinding stone retainer and said support frame.
 4. The grinding arrangement, as defined in claim 3, wherein said grinding arrangement further includes a support shaft; said support shaft being mounted to said frame; said grinding stone retainer being mounted fro movement along said support shaft; and said force measurement cell being mounted between said support shaft and said frame.
 5. The grinding arrangement, as defined in claim 1, wherein said grinding arrangement includes a grinding stone retainer holding said grinding stone; and said force measurement cell being inserted between said grinding stone retainer and said grinding stone.
 6. The grinding arrangement, as defined in claim 1, wherein said control arrangement includes a memory and a threshold force value being stored in said memory; and said control arrangement making an error signal available in the event that a measured value of said force measurement cell exceeds said threshold value.
 7. The grinding arrangement, as defined in claim 1, wherein said chopper arrangement is that of a forage harvester. 